Ex vivo Mesoscale human temporal lobe dataset

The human hippocampus is essential to cognition and emotional processing.
Its function is defined by its connectivity. Although some pathways have
been well-established, our knowledge about anterior-posterior connectivity
and the distribution of fibers from major fiber bundles remain limited.
Mesoscale (250 mm isotropic acquisition, upsampled to 125 mm) resolution
MR images of the human temporal lobe afforded a detailed visualization of
fiber tracts, including those that related anterior-posterior
substructures defined as subregions (head, body, tail) and subfields
(cornu ammonis 1-3, dentate gyrus) of the hippocampus. Fifty pathways were
dissected between the head and body, highlighting an intricate mesh of
connectivity between these two subregions. Along the body subregion, 12
lamellae were identified based on morphology and the presence of
interlamellar fibers that appear to connect neighboring lamellae at the
edge of the external limb of the granule cell layer (GCL). Translamellar
fibers (i.e. longitudinal fibers crossing more than 2 lamellae) were also
evident at the edge of the internal limb of the GCL. The dentate gyrus of
the body was the main site of connectivity with the fimbria. Unique
pathways were dissected within the fimbria that connected the body of the
hippocampus with the amygdala and the temporal pole. A topographical
segregation within the fimbria was determined by fibers’ hippocampal
origin, illustrating the importance of mapping the spatial distribution of
fibers. Elucidating the detailed structural connectivity of the
hippocampus is crucial to develop better diagnostic markers of
neurological and psychiatric conditions, as well as to devise novel
surgical interventions.